tournament.cc (13654:dc3878f03a0c) tournament.cc (13959:ea907b02c800)
1/*
2 * Copyright (c) 2011, 2014 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software

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44
45#include "base/bitfield.hh"
46#include "base/intmath.hh"
47
48TournamentBP::TournamentBP(const TournamentBPParams *params)
49 : BPredUnit(params),
50 localPredictorSize(params->localPredictorSize),
51 localCtrBits(params->localCtrBits),
1/*
2 * Copyright (c) 2011, 2014 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software

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44
45#include "base/bitfield.hh"
46#include "base/intmath.hh"
47
48TournamentBP::TournamentBP(const TournamentBPParams *params)
49 : BPredUnit(params),
50 localPredictorSize(params->localPredictorSize),
51 localCtrBits(params->localCtrBits),
52 localCtrs(localPredictorSize, SatCounter(localCtrBits)),
52 localHistoryTableSize(params->localHistoryTableSize),
53 localHistoryBits(ceilLog2(params->localPredictorSize)),
54 globalPredictorSize(params->globalPredictorSize),
55 globalCtrBits(params->globalCtrBits),
53 localHistoryTableSize(params->localHistoryTableSize),
54 localHistoryBits(ceilLog2(params->localPredictorSize)),
55 globalPredictorSize(params->globalPredictorSize),
56 globalCtrBits(params->globalCtrBits),
57 globalCtrs(globalPredictorSize, SatCounter(globalCtrBits)),
56 globalHistory(params->numThreads, 0),
57 globalHistoryBits(
58 ceilLog2(params->globalPredictorSize) >
59 ceilLog2(params->choicePredictorSize) ?
60 ceilLog2(params->globalPredictorSize) :
61 ceilLog2(params->choicePredictorSize)),
62 choicePredictorSize(params->choicePredictorSize),
58 globalHistory(params->numThreads, 0),
59 globalHistoryBits(
60 ceilLog2(params->globalPredictorSize) >
61 ceilLog2(params->choicePredictorSize) ?
62 ceilLog2(params->globalPredictorSize) :
63 ceilLog2(params->choicePredictorSize)),
64 choicePredictorSize(params->choicePredictorSize),
63 choiceCtrBits(params->choiceCtrBits)
65 choiceCtrBits(params->choiceCtrBits),
66 choiceCtrs(choicePredictorSize, SatCounter(choiceCtrBits))
64{
65 if (!isPowerOf2(localPredictorSize)) {
66 fatal("Invalid local predictor size!\n");
67 }
68
69 if (!isPowerOf2(globalPredictorSize)) {
70 fatal("Invalid global predictor size!\n");
71 }
72
67{
68 if (!isPowerOf2(localPredictorSize)) {
69 fatal("Invalid local predictor size!\n");
70 }
71
72 if (!isPowerOf2(globalPredictorSize)) {
73 fatal("Invalid global predictor size!\n");
74 }
75
73 //Set up the array of counters for the local predictor
74 localCtrs.resize(localPredictorSize);
75
76 for (int i = 0; i < localPredictorSize; ++i)
77 localCtrs[i].setBits(localCtrBits);
78
79 localPredictorMask = mask(localHistoryBits);
80
81 if (!isPowerOf2(localHistoryTableSize)) {
82 fatal("Invalid local history table size!\n");
83 }
84
85 //Setup the history table for the local table
86 localHistoryTable.resize(localHistoryTableSize);
87
88 for (int i = 0; i < localHistoryTableSize; ++i)
89 localHistoryTable[i] = 0;
90
76 localPredictorMask = mask(localHistoryBits);
77
78 if (!isPowerOf2(localHistoryTableSize)) {
79 fatal("Invalid local history table size!\n");
80 }
81
82 //Setup the history table for the local table
83 localHistoryTable.resize(localHistoryTableSize);
84
85 for (int i = 0; i < localHistoryTableSize; ++i)
86 localHistoryTable[i] = 0;
87
91 //Setup the array of counters for the global predictor
92 globalCtrs.resize(globalPredictorSize);
93
94 for (int i = 0; i < globalPredictorSize; ++i)
95 globalCtrs[i].setBits(globalCtrBits);
96
97 // Set up the global history mask
98 // this is equivalent to mask(log2(globalPredictorSize)
99 globalHistoryMask = globalPredictorSize - 1;
100
101 if (!isPowerOf2(choicePredictorSize)) {
102 fatal("Invalid choice predictor size!\n");
103 }
104
105 // Set up choiceHistoryMask
106 // this is equivalent to mask(log2(choicePredictorSize)
107 choiceHistoryMask = choicePredictorSize - 1;
108
88 // Set up the global history mask
89 // this is equivalent to mask(log2(globalPredictorSize)
90 globalHistoryMask = globalPredictorSize - 1;
91
92 if (!isPowerOf2(choicePredictorSize)) {
93 fatal("Invalid choice predictor size!\n");
94 }
95
96 // Set up choiceHistoryMask
97 // this is equivalent to mask(log2(choicePredictorSize)
98 choiceHistoryMask = choicePredictorSize - 1;
99
109 //Setup the array of counters for the choice predictor
110 choiceCtrs.resize(choicePredictorSize);
111
112 for (int i = 0; i < choicePredictorSize; ++i)
113 choiceCtrs[i].setBits(choiceCtrBits);
114
115 //Set up historyRegisterMask
116 historyRegisterMask = mask(globalHistoryBits);
117
118 //Check that predictors don't use more bits than they have available
119 if (globalHistoryMask > historyRegisterMask) {
120 fatal("Global predictor too large for global history bits!\n");
121 }
122 if (choiceHistoryMask > historyRegisterMask) {

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196
197 bool global_prediction;
198 bool choice_prediction;
199
200 //Lookup in the local predictor to get its branch prediction
201 local_history_idx = calcLocHistIdx(branch_addr);
202 local_predictor_idx = localHistoryTable[local_history_idx]
203 & localPredictorMask;
100 //Set up historyRegisterMask
101 historyRegisterMask = mask(globalHistoryBits);
102
103 //Check that predictors don't use more bits than they have available
104 if (globalHistoryMask > historyRegisterMask) {
105 fatal("Global predictor too large for global history bits!\n");
106 }
107 if (choiceHistoryMask > historyRegisterMask) {

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181
182 bool global_prediction;
183 bool choice_prediction;
184
185 //Lookup in the local predictor to get its branch prediction
186 local_history_idx = calcLocHistIdx(branch_addr);
187 local_predictor_idx = localHistoryTable[local_history_idx]
188 & localPredictorMask;
204 local_prediction = localCtrs[local_predictor_idx].read() > localThreshold;
189 local_prediction = localCtrs[local_predictor_idx] > localThreshold;
205
206 //Lookup in the global predictor to get its branch prediction
207 global_prediction = globalThreshold <
190
191 //Lookup in the global predictor to get its branch prediction
192 global_prediction = globalThreshold <
208 globalCtrs[globalHistory[tid] & globalHistoryMask].read();
193 globalCtrs[globalHistory[tid] & globalHistoryMask];
209
210 //Lookup in the choice predictor to see which one to use
211 choice_prediction = choiceThreshold <
194
195 //Lookup in the choice predictor to see which one to use
196 choice_prediction = choiceThreshold <
212 choiceCtrs[globalHistory[tid] & choiceHistoryMask].read();
197 choiceCtrs[globalHistory[tid] & choiceHistoryMask];
213
214 // Create BPHistory and pass it back to be recorded.
215 BPHistory *history = new BPHistory;
216 history->globalHistory = globalHistory[tid];
217 history->localPredTaken = local_prediction;
218 history->globalPredTaken = global_prediction;
219 history->globalUsed = choice_prediction;
220 history->localHistoryIdx = local_history_idx;

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303
304 assert(old_local_pred_index < localPredictorSize);
305
306 // Update the choice predictor to tell it which one was correct if
307 // there was a prediction.
308 if (history->localPredTaken != history->globalPredTaken &&
309 old_local_pred_valid)
310 {
198
199 // Create BPHistory and pass it back to be recorded.
200 BPHistory *history = new BPHistory;
201 history->globalHistory = globalHistory[tid];
202 history->localPredTaken = local_prediction;
203 history->globalPredTaken = global_prediction;
204 history->globalUsed = choice_prediction;
205 history->localHistoryIdx = local_history_idx;

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288
289 assert(old_local_pred_index < localPredictorSize);
290
291 // Update the choice predictor to tell it which one was correct if
292 // there was a prediction.
293 if (history->localPredTaken != history->globalPredTaken &&
294 old_local_pred_valid)
295 {
311 // If the local prediction matches the actual outcome,
312 // decrement the counter. Otherwise increment the
313 // counter.
314 unsigned choice_predictor_idx =
315 history->globalHistory & choiceHistoryMask;
316 if (history->localPredTaken == taken) {
317 choiceCtrs[choice_predictor_idx].decrement();
318 } else if (history->globalPredTaken == taken) {
319 choiceCtrs[choice_predictor_idx].increment();
320 }
296 // If the local prediction matches the actual outcome,
297 // decrement the counter. Otherwise increment the
298 // counter.
299 unsigned choice_predictor_idx =
300 history->globalHistory & choiceHistoryMask;
301 if (history->localPredTaken == taken) {
302 choiceCtrs[choice_predictor_idx]--;
303 } else if (history->globalPredTaken == taken) {
304 choiceCtrs[choice_predictor_idx]++;
305 }
321 }
322
323 // Update the counters with the proper
324 // resolution of the branch. Histories are updated
325 // speculatively, restored upon squash() calls, and
326 // recomputed upon update(squash = true) calls,
327 // so they do not need to be updated.
328 unsigned global_predictor_idx =
329 history->globalHistory & globalHistoryMask;
330 if (taken) {
306 }
307
308 // Update the counters with the proper
309 // resolution of the branch. Histories are updated
310 // speculatively, restored upon squash() calls, and
311 // recomputed upon update(squash = true) calls,
312 // so they do not need to be updated.
313 unsigned global_predictor_idx =
314 history->globalHistory & globalHistoryMask;
315 if (taken) {
331 globalCtrs[global_predictor_idx].increment();
332 if (old_local_pred_valid) {
333 localCtrs[old_local_pred_index].increment();
334 }
316 globalCtrs[global_predictor_idx]++;
317 if (old_local_pred_valid) {
318 localCtrs[old_local_pred_index]++;
319 }
335 } else {
320 } else {
336 globalCtrs[global_predictor_idx].decrement();
337 if (old_local_pred_valid) {
338 localCtrs[old_local_pred_index].decrement();
339 }
321 globalCtrs[global_predictor_idx]--;
322 if (old_local_pred_valid) {
323 localCtrs[old_local_pred_index]--;
324 }
340 }
341
342 // We're done with this history, now delete it.
343 delete history;
344}
345
346void
347TournamentBP::squash(ThreadID tid, void *bp_history)

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326
327 // We're done with this history, now delete it.
328 delete history;
329}
330
331void
332TournamentBP::squash(ThreadID tid, void *bp_history)

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